1. Field of the Invention
The present invention relates to a surface acoustic wave device for transducing an electric signal to a surface acoustic wave on a nonpiezoelectric plate having a piezoelectric substrate with at least an interdigital transducer.
2. Description of the Prior Art
Conventional methods for exciting an acoustic vibration on a nonpiezoelectric plate generally include a wedge-shaped transducer with a bulk wave vibrator for vibrating a nonpiezoelectric plate indirectly, or a piezoelectric thin film transducer for vibrating a nonpiezoelectric plate directly. The wedge-shaped transducer is mainly used for a non-destruction evaluation by ultrasound under a comparative low frequency operation alone because of the difficulty on manufacturing accuracy of the wedge angle and so on. The piezoelectric thin film transducer consists of a nonpiezoelectric plate, a piezoelectric thin film mounted on the nonpiezoelectric plate and made from ZnO and others, and interdigital transducers exciting the acoustic vibration on the nonpiezoelectric plate. Because of various transmission characteristics of the interdigital transducers with various structures, the piezoelectric thin film transducer is used as a high frequency device, however has operation frequencies limited to the UHF and VHF bands, and has some problems on manufacturing and mass production.
Thus, there are some problems on response time, sensitivity, durability, manufacturing, mass production, difficulty in use, operation frequencies, and high voltage operation with high power consumption in conventional transducers.